I broke my thumb at Glen Helen a while ago. I tore all the ligaments in it and had three nice big chunks of bone where they werent supposed to be. The bone and ligaments were reattached and I lost about 30% motion in it... anyway, my thumb is a lot weaker than it used to be.

I'm having trouble with my thumb cramping up... I've ridden with a thumb throttle since I started riding about 10 years ago, so I cant get used to a twist throttle. I've got a LoneStar 265R and I'm running a Keihin 38PWK carb and a stock thumb throttle (from 1986)... I'm thinking about buying a new Blaster throttle or something because my throttle is pretty wore out... But is there anything else I can do to ease the pull on the throttle? Maybe change the spring in the carb? Anything?

 

Maybe replace your cable, oil it up real good, clean all the other components like the carb and inside the thumb throttle, and cut a little off your spring. Or maybe check into getting an extension for your thumb throttle for more leverage.

 

Take the spring out of the carb and cut a coil off of it. Start w/ one coil then bend the sharp tip down w/ needle nose so it doesn't dig into the top of the carb. Stretch the spring out to the old size then reinstall. Don't cut to many coils off the spring or the throttle won't return to the closed position.

 

Check out www.lrdperformance.com
Look under "Racing Tips"!

 

Don't cut the spring...less coils traveling the same distance will increase the spring rate.
First start by polishing the slide bore with a felt buffing wheel on a dremal tool . Next sand or grind down the outside edges of the spring.. this makes the spring weeker and a lot easier to compress. Make sure you properly lube your cable and thumb linkage after witha good cable lube.

 

Cutting the springs works. I've done it more then once w/ great results each time..

 

so have I but sanding it works 10X better.
If you buy a weaker or stronger spring it comes with smaller dia. steel coils, not the same size with less number of coils